Synthetic polyamides are typically processed at temperatures around 270° C. or above, particularly in spinning processes. Heat resistance issues can arise at these temperatures in that polyamides are decomposed by the heat. Further deficiencies of polyamides often include their poor resistance to light, their poor stability in melt processing due to their susceptibility to oxidation, their poor thermal aging and their poor resistance to chemical and oxidative agencies.
Sterically hindered cyclic amines are widely used in industry as stabilizers of polymers. Starting materials of particular interest include isophthalic acid and aromatic derivatives which are used for preparing N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-benzenedicarboxamide or other sterically hindered cyclic amine derivatives. 4-Amino-2,2,6,6-tetramethylpiperidine (TAD) is a typical building block of what are known as HALS systems. TAD is obtainable in a continuous manner on a large industrial scale as described in EP0776887 B1 for example.
EP 1556350 B1 describes an optimized process for preparing N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3-benzenedicarboxamide.
However, the large scale industrial manufacture of the aromatic starting materials always proceeds from xylene, which is a petroleum derivative. Because petroleum sources are finite, it is advantageous to substitute “green” alternatives for this building block.